Add a != MIN/MAX_VALUE_CST ? CST-+1 : a to minmax_from_comparison

This patch adds the support for match that was implemented for PR 87913 in phiopt.
It implements it by adding support to minmax_from_comparison for the check.
It uses the range information if available which allows to produce MIN/MAX expression
when comparing against the lower/upper bound of the range instead of lower/upper
of the type.

minmax-20.c is the new testcase which tests the ranges part.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

gcc/ChangeLog:

	* fold-const.cc (minmax_from_comparison): Add support for NE_EXPR.
	* match.pd ((cond (cmp (convert1? x) c1) (convert2? x) c2) pattern):
	Add ne as a possible cmp.
	((a CMP b) ? minmax<a, c> : minmax<b, c> pattern): Likewise.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/minmax-22.c: New test.

3 files changed, 40 insertions, 2 deletions

diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 5752150..84b0d06 100644
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -173,6 +173,19 @@ minmax_from_comparison (tree_code cmp, tree exp0, tree exp1, tree exp2, tree exp
 	  /* X > Y - 1 equals to X >= Y.  */
 	  if (cmp == GT_EXPR)
 	    code = GE_EXPR;
+	  /* a != MIN_RANGE<a> ? a : MIN_RANGE<a>+1 -> MAX_EXPR<MIN_RANGE<a>+1, a> */
+	  if (cmp == NE_EXPR && TREE_CODE (exp0) == SSA_NAME)
+	    {
+	      value_range r;
+	      get_range_query (cfun)->range_of_expr (r, exp0);
+	      if (r.undefined_p ())
+		r.set_varying (TREE_TYPE (exp0));
+
+	      widest_int min = widest_int::from (r.lower_bound (),
+						 TYPE_SIGN (TREE_TYPE (exp0)));
+	      if (min == wi::to_widest (exp1))
+		code = MAX_EXPR;
+	    }
 	}
       if (wi::to_widest (exp1) == (wi::to_widest (exp3) + 1))
 	{
@@ -182,6 +195,19 @@ minmax_from_comparison (tree_code cmp, tree exp0, tree exp1, tree exp2, tree exp
 	  /* X >= Y + 1 equals to X > Y.  */
 	  if (cmp == GE_EXPR)
 	  code = GT_EXPR;
+	  /* a != MAX_RANGE<a> ? a : MAX_RANGE<a>-1 -> MIN_EXPR<MIN_RANGE<a>-1, a> */
+	  if (cmp == NE_EXPR && TREE_CODE (exp0) == SSA_NAME)
+	    {
+	      value_range r;
+	      get_range_query (cfun)->range_of_expr (r, exp0);
+	      if (r.undefined_p ())
+		r.set_varying (TREE_TYPE (exp0));
+
+	      widest_int max = widest_int::from (r.upper_bound (),
+						 TYPE_SIGN (TREE_TYPE (exp0)));
+	      if (max == wi::to_widest (exp1))
+		code = MIN_EXPR;
+	    }
 	}
     }
   if (code != ERROR_MARK
diff --git a/gcc/match.pd b/gcc/match.pd
index aae3649..16482b7 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -4833,7 +4833,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 
    Case 2)
    (cond (eq (convert1? x) c1) (convert2? x) c2) -> (cond (eq x c1) c1 c2).  */
-(for cmp (lt le gt ge eq)
+(for cmp (lt le gt ge eq ne)
  (simplify
   (cond (cmp (convert1? @1) INTEGER_CST@3) (convert2? @1) INTEGER_CST@2)
   (with
@@ -5024,7 +5024,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 /* Optimize (a CMP b) ? minmax<a, c> : minmax<b, c>
    to minmax<min/max<a, b>, c> */
 (for minmax (min max)
- (for cmp (lt le gt ge)
+ (for cmp (lt le gt ge ne)
   (simplify
    (cond (cmp @1 @3) (minmax:c @1 @4) (minmax:c @2 @4))
    (with
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-22.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-22.c
new file mode 100644
index 0000000..481c375
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-22.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-phiopt2" } */
+
+int f(int num)
+{
+  if (num < 3) __builtin_unreachable();
+  return num != 3 ?  num : 4;
+}
+
+/* In phiopt2 with the range information, this should be turned into
+   a MAX_EXPR.  */
+/* { dg-final { scan-tree-dump-times "MAX_EXPR" 1 "phiopt2" } } */